Electron-Beam-Induced Conduction in Polystyrene

The carrier mobilities of PS were studied using a short-pulsed electron-beam. Even in the polymer with a π-electron system, no clear knee was observed in the induced charge signals at low applied fields. A logarithmic plot of the induced current versus time gives a knee at time T r , which is thought to be the transit time of the carrier front between electrodes. Simple calculation by the formula µ= L / T r E gives an apparent carrier mobility µ of 2.5 × 10 -5 for electrons and 1.2 × 10 -5 cm 2 /Vsec for holes, at 293 K. These apparent mobilities are a little smaller than those (10 -4 –10 -5 cm 2 /Vsec) estimated from the knee point of the induced charge signal at higher fields in previous reports. Thus the measured mobility is field-independent and increases with temperature with an activation energy of about 0.4 eV for both electrons and holes.